Combustion apparatus



Nov. 27, 1934. L CORBETT 1,981,947

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COMBUSTION APPARATUS Filed Dec. 4, 1928 4 Sheets-Sheet 3 /M lzzberoforJaw-W4. )1? 001.5037

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Nov. 27, 1934. w. CQRBETT 1,981,947

COMBUSTI ON APPARATUS Filed Dec. 4, 1928 4 Sheets-Sheet 4 Patented Nov.27, 1934 UNITED STATES PATENT OFFICE COMBUSTION APPARATUS Doble,Hingham, Mass.

Application December 4, 1928, Serial No. 323,687

1 Claim.

This invention relates to combustion apparatus for burning solid fuel.

One object of the invention is to provide novel and improved combustionapparatus which is reliable in operation, requires minimum attention,

and may be substantially automatic in operation, and one which may besuccessfully operated utilizing any of the different grades of solidfuel.

A further and more specific object of the invention is to provide novelcombustion apparatus capable of successful use as an automatic stoker inheating apparatus, and whose construction is such as to insure efiicientcombustion of solid fuel in an automatic manner requiring minimumattention.

With these objects in view, and such others as may hereinafter appear,the invention consists in the combustion apparatus and in thestructures, arrangements and combinations of parts hereinafter describedand particularly defined in the claim at the end of this specification.

In the drawings the different features of the invention are illustratedas embodied in a domestic heating apparatus wherein Fig. 1 is a sideelevation of the apparatus with portions in section; Fig. 2 is a planview, with portions in section, of the apparatus shown in Fig. 1,; Fig.3 is an end elevation of the apparatus viewed from the right in Fig. 1;and Figs. 4 and 5 are details to be referred to.

In general, the present invention contemplates combustion apparatus forthe successful and economical combustion of the solid fuels such as thedifferent grades of bituminous and anthracite coal and coke and which abed of the fuel is maintained during combustion upon an inclined grateoperatively supported within a combustion chamber, by the supply ofsucceeding amounts of the fuel to the upper portion of the grate.Provision is made for imparting movement to the bed of fuel duringcombustion preferably by antomatic movement of the grate member.Provisicn is also made for forcing the primary supply of air through thefuel bed to maintain the combustion and also preferably an additionalsupply of air over the fuel bed in order to complete the combustion. Thegrate member may and preferably will be constructed of conical shape andthe fuel fed from below the grate member upwardly through an opening inthe apex portion of the cone to be thereby deposited upon the upperportion of the conical grate member. During combustion the movement ofthe gn'ate member together with gravity causes the progressive movementof the fire and ash down the inclined grate, and provision is preferablymade for automatically removing the ash as the latter accumulates at thelower portion of the grate.

Referring now to the drawings which illustrate the invention as embodiedin a domestic heating apparatus such as a hot water or steam heater,represents the heater whose general construction and operation may,except as to details to be hereinafter pointed out, comprise that of theordinary hot water or steam heater at present used for domestic heatingpurposes. The heater 10 is provided with the usual combustion chamber 12Within which a novel grate member 14 is operatively supported uponstandards 15, as illustrated in Fig. 1. The grate member 14 comprises amovable portion 17 preferably of conical shape, as illustrated in Fig.1, and which is operatively supported to be capable of rotary movementabout its vertical axis upon ball bearing members 20 supported within araceway formed by cooperating portions 21 in the underside of asupporting web 22 of the movable conical grate member, and an upstandingrim portion 23 of a stationary grate member 24, as shown in Fig. 1. Thestationary grate member 24 is arranged to surround the conical gratemember and is provided with a flaring rim portion 28 which serves, aswill be described, to support the lower portion of the fuel bed and todeflect the ashes from the lower portion of the conical grate memberdown into an annular trough 29 in the stationary grate memher.

In order to maintain a bed of the solid fuel upon the conical gratemember 14, as herein shown, provision is made for feeding a stream ofthe solid fuel from a storage hopper 30 through a fuel supply conduit orpipe 32, the latter being extended upwardly through an opening 34 in theapex portion of the conical grate member. The movement of the solid fuelfrom the hopper 30 is effected by a reciprocatory plunger or piston 36working in the end portion of the fuel supply pipe 32. The fuel supplyhopper 36 is preferably constructed with a downwardly inclined bottomwall 38 which insures flow of the solid fuel by gravity through anoutlet or discharge opening into the end portion of the fuel supply pipeand in advance of the piston 36. The piston 36 is arranged to bereciprocated. by a crank 40 and connecting rod 42, the crank beingsecured to a transversely extended shaft 44, and the latter is arrangedto be rotated by means of a crank 46, link 47 and pawl arm 48. The pawlarm 48 carries a pawl 49 which is arranged to cooperate with the teethof a ratchet 54 secured upon said shaft 44. The amount that the ratchet54 and shaft 44 is rotated at each throw of the pawl is variablycontrolled by a spring finger or member 106 mounted upon an operatingarm 108 loosely mounted upon the shaft 44 and arranged to cooperate withthe pawl 49 to control the number of teeth that the pawl will pick upand advance the ratchet at each throw of the pawl. The operating arm 108may and preferably will be connected with the air supply as will bedescribed. The crank 46 is driven from an electric motor 56 throughgearing connections indicated diagrammatically at 58.

From the description thus far and from an inspection of Fig. 1 it willbe apparent that in the operation of the combustion apparatus, as thesolid fuel is fed upwardly through the fuel supply pipe 32 it emergesfrom the open upper end thereof and overflows onto the conical grate. Inthis manner a bed of fuel of substantial thickness, depending upon therate of the fuel feed, is maintained upon the conical grate surface, thebed being supported at its lower end by the rim section of thestationary grate member 24.

Provision is made for forcing the primary supply' of air for maintainingthe combustion through the bed of fuel as the latter is supported uponthe conical grate, and as herein shown I than the inlet end thereof,thereby overcoming J any tendency of dust and ash to gravitate into theopening and to clog the same. Air under pressure is preferablysuppliedto within the' conical grate from a fan or blower 64 connectedto the motor 66 to be driven thereby and whose discharge pipe 65 isconnected by a conduit 66 to an opening formed in the supporting web 22of the conical grate member, as illustrated in Fig. 1. For conveniencethe conduit 66 may be arranged to surround the fuel feed pipe 32 forthat portion of the length of the same within the heater, and in thismanner an annular air passage is provided between the conduits 32 and66.

Provision is also preferably made for supplying additional air to abovethe bed of fuel during the combustion thereof in order that thevolatiles within the coal or other fuel which may have been distilledmay be burned as well as'in order to complete the combustion of the fuelgases themselves. As herein shown, the additional air is distributedover the fire from two end of the fuel supply pipe 32 and the movableconical grate 14. In order to deflect the air as it passes through suchannular opening in a direction downwardly over the surface of the fireto distribute the air through the mass of fuel gases, it is preferred toprovide the downwardly extended lip '76 upon the upper end of the fuelsupply pipe 32. In order that the combustion may approach completion itis desirable that approximately one-half of the total air should beadmitted over the fire through the openings 70 and the opening betweenthe fuel tube and the movable grate previously described. In additionsome additional air may find its way into I the combustion chamberthrough the lower rows of primary air openings 60 inasmuch as duringcombustion the extreme lowest portion of the grate will be covered withmaterial consisting mostly of ash so that the air passing therethroughis not consumed. The mass of coal or other fuel within the upper end ofthe fuel supply pipe ,serves as a diffuser for the additional airpassing therethrough, producing many small stream of air projected inrandom directions,

al'air in that inherent control of the additional air is attained bycontrol of the quantity of the primary air and by properly proportioningthe size and number of the various openings described, the proper amountof additional air will be supplied at all of the different rates. ofcombustion.

Provision is also preferably made in the illustrated apparatus forcontrolling the volume of both the primary and additional air inaccordance with the amount of fuel being fed, and as herein shown therate of fuel feed is controlled by regulating the position of a springfinger 106 (see Fig. 4) mounted upon an operating arm 108 provided witha handle 110 so that the pawl 49 will pick up a variable number of teethof the ratchet wheel 54 according to the particular position into whichthe operating arm and handle are moved. The operating arm is connectedby the linkage illustrated in Fig. 4 and indicated generally therein at112 to a damper 114 in the discharge pipe leading from the blower 64, sothat as the rate of fuel feed is increased, the volume of primary airand consequently the additional air is proportionately increased.

The rotary movement above described is preferably imparted to theconical grate member 14 by mechanism designed to provide rotation of theconical grate member upon its supporting bearings 20, and as hereinshown this movement is produced by the cooperation of a bevel piniongear 83 with a ring gear 84 formed in the under side of the supportingweb 22 of the grate member. The pinion gear 83 is mounted upon the endof a drive shaft 43 and is driven through mechanism including bevelgears 86, 87, a counter shaft 88, sprockets 89, 90, and a sprocket chain91, as best illustrated in Figs. 1 and 2. The rotary movement of theconical grate member 14 is preferably utilized to effect the automaticremoval of the ash as the latter accumulates in the trough 29 at thebottom of the conical grate member, and as herein shown scrapers 94formed as lugs on the lower portion of the grate member are arranged toextend to near the bottom of the trough 29 in a position such that asthe grate member rotates, each scraper 94 operates to scrape a portionof the ash into a position over an ash receiving opening 96 formed inthe supporting web 22 of the grate member. As the ash drops through theopening 96, it falls into an ash discharge pipe 97 having a driven wormconveyor 98 therein which operates to move the ash through the dischargepipe 97. From the discharge pipe 97 the ash is raised by a drivenendless conveyor of any usual or preferred form in; dicated generally at100 through the inclined conduit 102 to be discharged into an ashreceptacle 104, the latter preferably being provided with a cover at itsupper end to reduce dust to a minimum.

From the description thus far it will be apparent that the presentconstruction of combustion apparatus operates upon a principle analogousto the overfeed type of stoker which has been successfully used inindustrial Work and which has been found to be suitable for theefficient combustion of all different types'of coals. The ordinaryunderfeed stoker, particularly the type which has heretofore beenproposed for use in domestic heating apparatus, has not beensatisfactory With coals of either low fusion point ash, or coals of highash content, for the reason that during the operation of the stoker thecoal is fed and the ash removed in such manner that the ash is incontact with a highly incandescent fuel bed and is fused into clinkers.The present construction of conical grate serves to keep the burningfuel and the ash moving toward the point of ash discharge, andfurthermore as the concentration of ash increases, the ash is moved intoa region of lower temperature, thereby avoiding a tendency toward theformation of clinkers. This is an important advantage in a domesticheating apparatus, particularly in that it enables the operation of suchdomestic heating apparatus to be made substantially automatic.

By reference to Fig. 1 it will be observed that during the operation ofthe present combustion apparatus the movement of the fuel bed tends toovercome any caking which may occur as the coal leaves the fuel tube inthe region of lower temperature surrounding the coal tube. Any cakingwhich may take place is broken up by the movement of the fire with theconical grate. In

addition to its eifect in preventing caking and thereby enabling cakingand bituminous coals to be successfully burned in the present combustionapparatus, the moving rate in combination with its inclined position andparticularly with its conical shape assists the travel of the fire downthe sides of the cone. With relation to the intermediate movable conicalgrate member 14, both the fuel entering from the feed tube and thecircular stationary grate 24 are stationary and as a result duringoperation, the fuel bed between these two stationary elements is movedby the grate and the interaction tends to loosen the fire causing it toslide down the grate. A further result of this action is that theagitation of the fire causes the ash to fall downwardly toward the grateitself and into a region of lower temperature, thus contributing to theprevention of the formation of clinker.

By feeding the fuel in the manner described at the upper end of thegrate, the combustion occuring in the area surrounding the fuel tubewill be very slight, and as a result during operation a region of lowtemperature will prevail at this point so that the volatile portions ofthe fuel will be distilled at a low temperature avoiding cracking withthe formation of soot and. at the same time enabling the volatiles to bemixed with an excess of oxygen, thus insuring their complete combustion.The construction of the present combustion apparatus facilitates theinstallation of it in small size units such as in the domestic heaters,in that all tubes and mechanism entering the furnace may do so throughone opening enabling the apparatus to be readily installed in existingheaters, and the fact that the fuel may be successfully fed from belowthe grate, lowers the storage hopper, thus reducing the height to whichthe fuel must be lifted in charging the hopper.

While in the preferred and illustrated embodiment of the invention it ispreferred to utilize a forced draft for effecting movement of the airthrough the fuel bed and for supplying the additional air to thecombustion chamber above the fuel bed, nevertheless it is to beunderstood that in some instances if found desirable a natural draft, asby a chimney, may be utilized for effecting such air movement and airsupply, and furthermore it is to be understood that while it ispreferred to rotate the conical grate member as above described,nevertheless if found of advantage other forms of motion may be impartedto said grate member including oscillatory motion.

For the combustion of certain kinds of fuel such as certain finelydivided bituminous coals which exhibit a tendency toward packing, it maybe desirable to provide a mechanical feed for the fuel through the fuelsupply tube 32, such a construction being illustrated in detail in Fig.5. Referring to Fig. 5 the fuel supply tube is provided with a screwconveyor 130 driven from the shaft 44 through a pair of bevel gears 132,133. The upper end of the fuel supply tube 32 is preferably arranged totaper, as illustrated, in order to diminish any tendency which may existfor the fuel to pack as it is forced up through the end of the tube.

While the preferred form of the invention has been illustrated anddescribed, it will be understood that the same may be embodied in otherforms within the scope of the following claim.

Having thus described the invention, what is claimed is:-

In a combustion apparatus, in combination, a combustion chamber, aburner unit in the chamber comprising an annular stationary grate memberprovided with an upwardly and outwardly flaring rim portion and aninwardly extending flange forming a trough within said rim portion, aconical gratemember rotatably mounted upon and supported by the flangeof said stationary grate member and provided with a plurality ofopenings in and distributed around the surface thereof for permittingthe passage of a primary air supply through a conical bed of fuelsupported on the grate member, means for rotating the conical gratemember, scraper means carried by said conical grate member for assistingin the removal of ash accumulating in the aforesaid trough, means forsupplying air under pressure to within the conical grate member, andmeans for supplying fuel to the upper portion of the conical gratemember and maintaining a conical bed of fuel thereon.

LAWRENCE W. CORBET'I'.

